The present invention relates to liquid 1,3-phenylene diisocyanate (PDI), 1,1'-biphenyl diisocyanate (BPDI) and 1,1'-oxy-bis-(isocyanato-benzene)(OIB). More specifically, the present invention relates to liquid allophanate-modified prepolymers of PDI, BPDI and OIB and processes for their production and use.
Liquid methylene diphenyl diisocyanates are generally known in the art. U.S. Pat. No. 3,644,457, for example, discloses room temperature, stable, liquid isocyanates prepared by reacting one mole of diphenylmethane diisocyanate with 0.1 to 0.3 mols of poly-1,2-propylene ether glycol.
U.S. Pat. No. 4,738,991 discloses organic polyisocyanates characterized by allophanate linkages which are prepared by reacting an organic polyisocyanate with a poly- or monohydric alcohol in the presence of an organo-metallic catalyst. The catalyst is then deactivated with a compound such as an inorganic acid, organic acid, organic chloroformate or an organic acid chloride.
U.S. Pat. No. 4,866,103 discloses a polyisocyanate composition useful for producing elastomers in a RIM process. The disclosed polyisocyanate composition is the reaction product of (a) an alcohol and/or thiol having an average functionality of from about 1.5 to about 4 and an average equivalent weight of at least 500 with (b) at least 2 equivalents per hydroxyl and/or thiol equivalent of an organic polyisocyanate under conditions such that at least about 20% of the initially formed urethane and/or thiourethane groups are converted to allophanate and/or thioallophanate groups.
Other prior art relating to the preparation of allophanates which contain isocyanate groups includes British Patent 994,890 which teaches the reaction of urethane group containing isocyanates with excess diisocyanate either by heating the isocyanate alone or in the presence of a catalyst (e.g., a metal carboxylate, a metal chelate or a tertiary amine). This heating is continued until the isocyanate content is reduced to theoretical (i.e., the level at which theoretically complete reaction of the urethane groups is achieved).
U.S. Pat. No. 4,160,080 discloses a process for producing allophanate containing aliphatically and/or cycloaliphatically bound isocyanate groups in which compounds containing urethane groups are reacted with polyisocyanates having aliphatic and/or cycloaliphatic isocyanate groups in the presence of a strong acid. The process is generally conducted at a temperature of from 90.degree. C. to 140.degree. C. for about 4 to 20 hours.
Japanese Patent Application No. 1971-99176 discloses a method for preparing liquid diphenylmethane diisocyanate in which diphenylmethane diisocyanate is reacted with an aliphatic monovalent alcohol.
U.S. Pat. No. 5,319,053 discloses liquid diphenylmethane diisocyanate prepolymers having an NCO content of from 12 to 32.5% which are the reaction products of an aliphatic alcohol and diphenylmethane diisocyanate.
U.S. Pat. No. 5,319,054 discloses a process for the production of liquid methylene diphenyl diisocyanate in which one equivalent of a diisocyanate and one equivalent of an aliphatic alcohol are reacted to form a diurethane. This diurethane is then reacted with an isomeric mixture of diphenylmethane diisocyanate in an amount sufficient to generate an allophanate having an isocyanate group content of from about 12.0 to about 30.0%.
The prior art does not, however, disclose a process for producing a storage stable, liquid 1,3-phenylene diisocyanate, or 1,1'-biphenyl diisocyanate or 1,1'-oxy-bis-(isocyanato benzene).